A basic function of radiative systems such as sonar or radar is to reliably correlate echoes received from an object scanned from different locations. This permits identification, classification, or imaging of objects or surfaces, examples of which might be, in a marine environment, sea shells, pebbles, rocks, shoals, patches of seafloor, terrain, naval mines, undersea pipes or cables, or sunken vessels. Unfortunately, echo signature varies with the angle of incidence, or grazing angle, at which the object is scanned, which means that echoes received back from the same object at different grazing angles will correlate poorly. In particular, increasing grazing angle progressively foreshortens the apparent size of an object along the line of sight between the sonar/radar generator and the object. This in turn changes the frequency of radiation necessary to duplicate the signature of the object, requiring different frequencies for different grazing angles.